Suspension assembly having a microactuator grounded to a flexure

ABSTRACT

Disclosed is a suspension assembly for a disk drive that includes: a mounting plate having a through-hole; a microactuator mounted on the mounting plate; a flexure attached to the mounting plate, the flexure including a trace layer that includes a ground trace; and a conductive epoxy bonded to the microactuator extending through the through-hole to bond to the flexure, wherein the epoxy extends to the ground trace of the flexure such that the microactuator is grounded to the flexure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/146,710 filed on Jan. 2, 2014, entitled “SUSPENSION ASSEMBLY HAVING AMICROACTUATOR GROUNDED TO A FLEXURE” to Wing Chun Shum et al., which isa continuation of U.S. application Ser. No. 12/827,813 filed on Jun. 30,2010, entitled “SUSPENSION ASSEMBLY HAVING A MICROACTUATOR GROUNDED TO AFLEXURE” to Wing Chun Shum et al., both of which are hereby incorporatedby reference in their entirety.

BACKGROUND

Information storage devices are used to retrieve and/or store data incomputers and other consumer electronics devices. A magnetic hard diskdrive is an example of an information storage device that includes oneor more heads that can both read and write, but other informationstorage devices also include heads—sometimes including heads that cannotwrite. For convenience, all heads that can read are referred to as “readheads” herein, regardless of other devices and functions the read headmay also perform (e.g. writing, flying height control, touch downdetection, lapping control, etc).

In a modern magnetic hard disk drive device, each read head is asub-component of a head gimbal assembly (HGA). The read head typicallyincludes a slider and a read/write transducer. The read/write transducertypically comprises a magneto-resistive read element (e.g. so-calledgiant magneto-resistive read element, or a tunneling magneto-resistiveread element) and an inductive write structure comprising a flat coildeposited by photolithography and a yoke structure having pole tips thatface a disk media.

The HGA typically also includes a suspension assembly that includes amounting plate, a load beam, and a laminated flexure to carry theelectrical signals to and from the read head. The read head is typicallybonded to a tongue feature of the laminated flexure. The HGA, in turn,is a sub-component of a head stack assembly (HSA) that typicallyincludes a plurality of HGAs, a rotary actuator, and a flex cable. Themounting plate of each suspension assembly is attached to an arm of therotary actuator (e.g. by swaging), and each of the laminated flexuresincludes a flexure tail that is electrically connected to the HSA's flexcable (e.g. by solder bonding).

Modern laminated flexures typically include electrically conductivecopper traces that are isolated from a stainless steel support layer bya polyimide dielectric layer. So that the signals from/to the head canreach the flex cable on the actuator body, each HGA flexure includes aflexure tail that extends away from the head along the actuator arm andultimately attaches to the flex cable adjacent the actuator body. Thatis, the flexure includes electrically conductive traces that areelectrically connected to a plurality of electrically conductive bondingpads on the head, and extend from adjacent the head to terminate atelectrical connection points at the flexure tail.

The position of the HSA relative to the spinning disks in a disk drive,and therefore the position of the read heads relative to data tracks onthe disks, is actively controlled by the rotary actuator which istypically driven by a voice coil motor (VCM). Specifically, electricalcurrent passed through a coil of the VCM applies a torque to the rotaryactuator, so that the read head can seek and follow desired data trackson the spinning disk.

However, the industry trend towards increasing areal data density hasnecessitated substantial reduction in the spacing between data tracks onthe disk. Also, disk drive performance requirements, especiallyrequirements pertaining to the time required to access desired data,have not allowed the rotational speed of the disk to be reduced. Infact, for many disk drive applications, the rotational speed has beensignificantly increased. A consequence of these trends is that increasedbandwidth is required for servo control of the read head positionrelative to data tracks on the spinning disk.

One solution that has been proposed in the art to increase disk driveservo bandwidth is dual-stage actuation. Under the dual-stage actuationconcept, the rotary actuator that is driven by the VCM is employed as acoarse actuator (for large adjustments in the HSA position relative tothe disk), while a so-called “microactuator” having higher bandwidth butlesser stroke is used as a fine actuator (for smaller adjustments in theread head position). Various microactuator designs have been proposed inthe art for the purpose of dual-stage actuation in disk driveapplications. Some of these designs utilize one or more piezoelectricmicroactuators that are affixed to a stainless steel component of thesuspension assembly (e.g. the mounting plate or an extension thereof,and/or the load beam or an extension thereof, and/or an intermediatestainless steel part connecting the mounting plate to the load beam).

However, if the microactuator is electrically connected to a stainlesssteel surface of the suspension assembly (e.g. for grounding), anelectrochemical reaction may cause an oxidation layer to form on thestainless steel at the connection location. The oxidation layer may beinsulative and interfere with desired electrical conduction, and may beexacerbated by hot and humid conditions. Over time, the desired responseof the microactuator to applied signals may become diminished, leadingto reduced or impaired performance of the information storage deviceand/or data loss.

Therefore, there is a need in the information storage device arts for asuspension assembly design that can improve integration with amicroactuator by improving the grounding of the microactuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is top view of a disk drive that is capable of including anembodiment of the invention.

FIG. 2 is a bottom perspective view of the head gimbal assembly (HGA).

FIG. 3 is a top view of a portion of the HGA, according to oneembodiment of the invention.

FIG. 4 is a bottom view of a portion of the HGA, according to oneembodiment of the invention,

FIG. 5 is a cross-sectional view illustrating the epoxy extendingthrough the mounting plate and through the holes of the flexure toground to the flexure, according to one embodiment of the invention.

FIG. 6 is a cross-sectional view illustrating the epoxy extendingthrough the flexure to ground to the flexure, according to oneembodiment of the invention.

FIG. 7 is a cross-sectional view illustrating the epoxy extendingthrough the mounting plate and to the flexure and particularlyillustrates an air gap, according to one embodiment of the invention.

FIG. 8 is a schematic diagram of the flexure metal layer including anair gap, according to one embodiment of the invention.

FIG. 9 is a schematic diagram of the bottom-side of the load beamincluding an air gap, according to one embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 is top view of a disk drive 100 that is capable of including anembodiment of the present invention. The disk drive 100 includes a diskdrive base 102. The disk drive 100 further includes a spindle 106,rotably mounted on the disk drive base 102, for rotating a disk 104 thatis mounted on the spindle 106. The rotation of the disks 104 establishesair flow through optional recirculation filter 108. In certainembodiments, disk drive 100 may have only a single disk 104, oralternatively, two or more disks.

The disk drive 100 further includes a rotary coarse actuator 110 that isrotably mounted on disk drive base 102. The rotary coarse actuator 110includes an actuator arm 114 that supports a head gimbal assembly (HGA)118. Voice coil motor 112 rotates the actuator 110 through a limitedangular range so that the HGA 118 may be desirably positioned relativeto one or more tracks of information on the disk 104. Preferably thedisk drive 100 will include one HGA 118 per disk surface, butdepopulated disk drives are also contemplated in which fewer HGAs areused. Under non-operating conditions the HGAs may be parked on ramp 120,for example to avoid contact with the disk 104 when it is not spinning.Electrical signals to/from the HGA 118 are carried to other driveelectronics, in part via a flex cable (not shown) and a flex cablebracket 116.

FIG. 2 is a bottom perspective view of an HGA 200. Referringadditionally to FIG. 2, the HGA 200 includes a load beam 202, and a readhead 210 for reading and writing data from and to a magnetic disk (e.g.disk 104). The read head 210 includes a slider substrate having an airbearing surface (the label 210 points to this surface) and an opposingtop surface (not visible in the view of FIG. 2). The slider substratepreferably comprises AlTiC, although another ceramic or silicon mightalso be used. The slider substrate of the read head 210 also includes atrailing face 212 that includes a read/write transducer (too small to bepractically shown in the view of FIG. 2, but disposed on the trailingface 212). In certain embodiments, the read/write transducer ispreferably an inductive magnetic write transducer merged with amagneto-resistive read transducer. The purpose of the load beam 202 isto provide limited vertical compliance for the read head 210 to followvertical undulations of the surface of a disk (e.g. disk 104 of FIG. 1)as it rotates, and to preload the air bearing surface of the read head210 against the disk surface by a preload force that is commonlyreferred to as the “gram load.”

In the embodiment of FIG. 2, the HGA 200 also includes a laminatedflexure 204 attached to the load beam 202. The laminated flexure 204includes a tongue 206 that has a read head bonding surface. The head 210is attached to the read head bonding surface of the tongue 206 of thelaminated flexure 204. Only a portion of the tongue 206 is visible inthe view of FIG. 2 because the read head 210 partially obscures it. Afirst purpose of the laminated flexure 204 is to provide compliance forthe head 210 to follow pitch and roll angular undulations of the surfaceof the disk (e.g. disk 104) as it rotates, while restricting relativemotion between the read head 210 and the load beam 202 in the lateraldirection and about a yaw axis. A second purpose of the laminatedflexure 204 is to provide a plurality of electrical paths to facilitatesignal transmission to/from the read head 210. For that second purpose,the laminated flexure 204 includes a plurality of electricallyconductive traces 218 that are defined in an electrically conductive(e.g. copper) sub-layer of the laminated flexure 204. Electricallyconductive traces 218 are isolated from a support layer (e.g. stainlesssteel) by a dielectric layer (e.g. polyimide).

In the embodiment of FIG. 2, the load beam 202 includes hinge plates 222and 224, and is attached to a mounting plate 220 via the hinge plates222 and 224 and a microactuator mounting structure 300. These componentsmay be made of stainless steel, and their attachments to each other maybe made by a plurality of spot welds, for example. Alternatively, theload beam 202 may have integral hinge plate regions rather than beingassembled with separate hinge plate components, so that the load beam202 and its hinge plates would be a single component having materialcontinuity. In another alternative, the microactuator mounting structure300 can also be an integral part of the mounting plate 220.

The load beam 202 with its hinge plates 222, 224 (if any), themicroactuator mounting structure 300, and the mounting plate 220, maytogether be referred to as a “suspension assembly.” Accordingly, themounting plate 220 may also be referred to as a suspension assemblymounting plate 220. In certain preferred embodiments, the suspensionassembly mounting plate 220 includes a swage boss 226 to facilitateattachment of the suspension assembly to an actuator arm (e.g. actuatorarm 114). In that case, the suspension assembly mounting plate 220 mayalso be referred to as a “swage mounting plate.” Note that, after thelaminated flexure 204 is attached to the load beam 202, the laminatedflexure 204 may be considered to also pertain to the “suspensionassembly.”

FIG. 3 is a top view of a portion of the HGA, according to oneembodiment of the invention. The suspension assembly 300 of the HGAincludes a mounting plate 304. The mounting plate 304 may include aswage tower 305 to facilitate attachment of the mounting platesuspension assembly to an actuator arm (e.g. actuator arm 114). Themounting plate 304 may have a through-hole 306 extending from a top-side307 of the mounting plate 304 to a bottom-side of the mounting plate. Aswill be described, in one embodiment, a microactuator mounting structure(340, 342) is formed in the mounting plate 304 and a microactuator (312,313) may be mounted in the microactuator mounting structure 304. Anepoxy 329 may be mounted to a microactuator and may extend through thethrough-hole 306 to bond to a flexure, in which, the epoxy 329 extendsthrough an opening of the flexure to a ground trace of the flexure suchthat the microactuator is grounded to the flexure.

In particular, mounting plate 304 may include a pair of approximatelysquare-shaped microactuator mounting structures 340 and 342 that areformed in the mounting plate 304. Microactuators 312 and 313 may each bemounted in a microactuator mounting structure 340 and 342, respectively.As is known in the art, microactuators are typically used to position aread head. Further, epoxy lines 330 and 332 of epoxy 329 may each bebonded to a microactuator and may extend through the through-hole 306 tobond to a flexure, in which, the epoxy 329 extends through an opening ofthe flexure to a gold-plated ground trace of the flexure such that themicroactuator is grounded to the flexure. It should be appreciated tothose of skill in the art that a single microactuator may be mounted tothe mounting plate, a pair of microactuators may be mounted to themounting plate, or any suitable number of microactuators may be mountedto the mounting plate.

With reference also to FIG. 4, which is a bottom view of a portion ofthe HGA, according to one embodiment of the invention, the through-hole306 extends from the top-side 307 of the mounting plate 304 to thebottom-side 309 of the mounting plate 304. Further, as can be seen onthe bottom-side 309 of the mounting plate 304, flexure 204 is attachedto the bottom-side 309 of the mounting plate 304 and flexure 204 iscoupled to the microactuators 312 and 313. As will be described in moredetail hereinafter, the flexure 204 may include a metal layer, aninsulator layer, a trace layer which includes a ground trace, and anopening, wherein the opening extends through the metal layer and theinsulator layer to a gold-plated ground trace of the flexure.

Thus, in one embodiment, a pair of epoxy lines 330 and 332 of epoxy 329may be bonded to the microactuators 312 and 313 and may extend throughthe through-hole 306 to bond to the flexure 204. In particular, as willbe described in more detail hereinafter, the epoxy 329 may extendthrough an opening of the flexure to the ground trace of the flexuresuch that the microactuator 312 and 313 are grounded to the flexure 204.

In one embodiment, the microactuators 312 and 313 are piezoelectric(PZT) microactuators. The piezoelectric microactuators 312 and 313 maybe gold (Au) plated. Further, in one embodiment, the epoxy 329 mayinclude silver (Ag) and is conductive. However, it should be appreciatedthat any sort of suitable epoxy or solder that is conductive may beutilized.

With reference now to FIG. 5, FIG. 5 illustrates a cross-sectional view500 of the epoxy extending through the mounting plate through the holesof the flexure to ground to the flexure, according to one embodiment ofthe invention. In particular, looking at FIG. 5, epoxy 502 extendsthrough the through-hole 503 of mounting plate 504 and through load beam506 to extend through an opening 507 of the flexure, and particularly,extends through the steel layer 508 and the insulator layer 512 of theflexure to bond to the gold-plated 520 copper layer 514 of the flexure,which is the ground trace. In this way, microactuators 312 and 313through epoxy 502 are grounded to the gold-plated ground trace of thecopper layer 514 of the flexure.

With reference also to FIG. 6, FIG. 6 illustrates a cross-sectional view600 of the epoxy 502 extending through the flexure 204 to ground to theflexure 204, according to one embodiment of the invention. As previouslydescribed, in one embodiment, the metal layer 508 of the flexure 204 maybe stainless steel and the insulator layer 512 may be a polyimide.Further, as shown in FIG. 6, flexure 204 may include a gold-plated 520copper layer 514 that includes a ground trace. As previously described,copper layer 514 of flexure 204 may include a plurality of conductivetraces and a ground trace. Further, the ground trace of the copper layer514 may be grounded by a via 519 to the steel layer 508. Also, has beenpreviously described, with reference to the functions of the flexure204, the read head is typically electrically connected to one or more ofthe pluralities of conductive traces of the copper layer 514.

Thus, in one embodiment, an Ag epoxy 502 may be used to ground themicroactuators by extending from the microactuators through athrough-hole of the mounting plate 504 and through an opening 507 of theflexure 204 to extend through the steel layer 508 and the insulatorlayer 512 of the flexure 204 to ground to the ground trace of theexposed gold-plated 520 copper layer 514 of the flexure. Accordingly,there is a direct grounding of the microactuators to the ground trace ofthe flexure by simply extending an epoxy through a through-hole of themounting plate. This is advantageous in that it solves problemsassociated with microactuators that are currently being bonded to thesteel of the mounting plate and does so utilizing the current flexurecable with virtually no additional cost or design/process changes.

Additional embodiments are hereinafter described to let air out so thatepoxy can flow down more easily to more easily contact the gold-platedcopper layer. FIG. 7 is a cross-sectional view 700 illustrating theepoxy 502 extending through the mounting plate 504 and into the flexureand particularly illustrates an air gap, according to another embodimentof the invention. In this embodiment, the epoxy 502 extends through themounting plate 504, the load beam 506, the steel layer 508, and theinsulator layer 512 to the gold-plated 520 copper layer 514. However,this embodiment includes an air hole or gap 710 formed in thegold-plated 520 copper layer 514 to allow for air flow. In oneembodiment, a cover 702 that may be formed from a thin insulatormaterial is present. By having the air hole, air is let out so that theepoxy 502 can flow down more easily to more easily contact thegold-plated 520 copper layer 514. Without the air hole, air bubbles mayform preventing the epoxy from more completely covering and contactingthe gold-plated copper layer.

Turning to FIG. 8, a schematic diagram of the flexure metal layer 800 isshown. In particular, FIG. 8 illustrates that gaps 802 may be formed inthe metal layer 508 of the flexure 204 adjacent the metal load beamlayer 506 to allow for air flow. With reference to FIG. 9, a schematicdiagram of the bottom-side of the load beam 900 is illustrated. As canbe seen in FIG. 9, the metal load beam layer 506 may include a gap 902to let air flow out. These additional embodiments aid in letting airflow out so that the epoxy can flow down more easily to more easilycontact the gold-plated copper layer, as previously described.

In the foregoing specification, the invention is described withreference to specific exemplary embodiments, but those skilled in theart will recognize that the invention is not limited to those. It iscontemplated that various features and aspects of the invention may beused individually or jointly and possibly in a different environment orapplication. The specification and drawings are, accordingly, to beregarded as illustrative and exemplary rather than restrictive.“Comprising,” “including,” and “having,” are intended to be open-endedterms.

What is claimed is:
 1. A suspension assembly comprising: a mountingplate having a through-hole; a microactuator mounted on the mountingplate; a flexure attached to the mounting plate, the flexure including:a trace layer that includes a ground trace, and a metal layer, whereinthe ground trace is grounded to the metal layer; and a conductive epoxybonded to the microactuator extending through the through-hole to bondto the flexure, wherein the epoxy extends to the ground trace of theflexure such that the microactuator is grounded to the flexure.
 2. Thesuspension assembly of claim 1 further comprising a plurality ofmicroactuators, each microactuator mounted in a respective microactuatormounting structure of the mounting plate, the epoxy being bonded to eachof the microactuators and extending through the through-hole to bond tothe flexure.
 3. The suspension assembly of claim 1 wherein themicroactuator is a piezoelectric microactuator.
 4. The suspensionassembly of claim 3 wherein the piezoelectric microactuator is gold (Au)plated.
 5. The suspension assembly of claim 1 wherein the epoxy issilver (Ag).
 6. The suspension assembly of claim 1 wherein the flexurefurther comprises an insulator layer.
 7. The suspension assembly ofclaim 6 wherein the metal layer comprises stainless steel and theinsulator layer comprises a polyimide.
 8. The suspension assembly ofclaim 6 wherein the metal layer includes a gap to allow for air flow. 9.The suspension assembly of claim 6 wherein the flexure further comprisesan opening in the metal layer and the insulator layer, wherein theopening extends through the metal layer and the insulator layer to theground trace.
 10. The suspension assembly of claim 9 wherein the epoxyextends through the opening.
 11. The suspension assembly of claim 6wherein the flexure further comprises a copper layer that includes theground trace and a plurality of conductive traces.
 12. The suspensionassembly of claim 11 wherein the copper layer is gold (Au) plated suchthat the epoxy extends from a gold plating of the microactuator to thegold plated copper layer.
 13. The suspension assembly of claim 11wherein the microactuator is configured to position a read head, andwherein the read head is electrically connected to one or more of theplurality of conductive traces.
 14. The suspension assembly of claim 11further comprising an air-hole formed through the copper layer to allowfor air flow.
 15. The suspension assembly of claim 1 wherein a load beamof the mounting plate includes a gap to allow for air flow.
 16. Thesuspension assembly of claim 1 wherein the ground trace is gold plated.